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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03-12-2014 to 17-12-2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed under GLP. All relevant validity criteria were met.
Qualifier:
according to guideline
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
inspected: June 2013; signature: November 2013
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
photometric method
Type:
log Pow
Partition coefficient:
>= 3.48 - <= 3.53
Temp.:
22.8 °C
pH:
7
Remarks on result:
other: Two chromatographic peaks at the associated Partition Coefficient values

HPLC method

The mean void time (t0) was determined to be 0.511 minutes.

The results of the HPLC method are given in the Table 3. The calibration curves of the log k’ of the reference substances as function of log Pow had an regression line represented by the equations:

Calibration 1: log k’ = 1.642 × log Pow + 1.2327 (r = 0.9979, n = 6 and r2 = 0.9959).

Calibration 2: log k’ = 1.640 × log Pow + 1.2366 (r = 0.9979, n = 6 and r2 = 0.9959).

 

Table 2. Calibration data

Reference Item

Log P

1stCalibration

2ndCalibration

 

 

tr1 /min

k

Log K

tr2 / min

k

Log k

Atrazine

2.6

4.067

6.959

0.843

4.061

6.947

0.842

2,3-Dichloroaniline

2.8

5.072

8.926

0.951

5.062

8.906

0.950

Diphenylamin

3.4

10.885

20.301

1.308

10.859

20.250

1.306

Phenyl benzoate

3.6

14.364

27.110

1.433

14.355

27.092

1.433

Biphenyl

4.0

27.919

53.636

1.729

27.883

53.566

1.729

1,2,4-Tricholorobenzene

4.2

31.191

60.039

1.778

31.190

60.037

1.778

tR1 Retention time 1. Injection

tR2 Retention time 2. Injection

k Capacity factor reference item

log Pow Decadic logarithm of the Partition Coefficient (n-octanol / water)

 

Table 3. Test item determination – peak 1 and peak 2

 

tr / min

k

Log k

Log P

Peak 1

 

 

 

1stCalibration

2ndCalibratrion

 

12.418

23.301

1.37

 

 

 

12.415

23.295

1.37

3.48 ± 0.02

3.43 to 3.53 (95% CI)

3.48 ± 0.02

3.43 to 3.54 (95% CI)

Mean

12.417

23.298

1.37

3.48

 

 

 

 

 

Peak 2

 

 

 

1stCalibration

2ndCalibratrion

 

13.273

24.975

1.40

 

 

 

13.267

24.963

1.40

3.53 ± 0.02

3.48 to 3.58 (95% CI)

3.53 ± 0.02

3.48 to 3.59 (95% CI)

Mean

13.270

24.969

1.40

3.53

 

tR : Retention time

k : Capacity factor test item

Pow : Partition Coefficient (n-octanol / water)

CI : Confidence Interval

Conclusions:
The partition coefficient of the test substance was determined to be log Pow = 3.48 – 3.53 at 22.8 °C and ca. pH 7.0
Executive summary:

The n-octanol/water partition coefficient was determined using the HPLC method within OECD TG 117 and EU Method A.8. The test was performed with a concentration of 50 mg test item/L in 60% methanol : 40% HPLC water. Samples of the test item were analysed via HPLC on a C18 column with diode array detection. Calibration was performed using six reference items with known log POW values (given by the guidelines). The reference items were measured twice, once before and once after the measurement of the test item, for which one replicate was double injected. The void time of the HPLC system was determined with sodium nitrate. Two individual log POW values for each of the two chromatographic resolved test item signals were derived under consideration of the first and second calibration and the analytically resolved chromatographic peaks. Finally, a mean value was calculated from these individual log Pow values. The log Pow was 3.48 (peak 1) to 3.53 (peak 2) in duplicate. The partition coefficient of the test substance was determined to be log Pow = 3.48 to 3.53 at mean temperature 22.8 °C and approximately neutral pH.

Description of key information

log Pow = 3.48 to 3.53 (range of peak values) at 22.8 °C and ca. pH 7.0, OECD TG 117, 2015

Key value for chemical safety assessment

Additional information

The n-octanol/water partition coefficient was determined using the HPLC method within OECD TG 117 and EU Method A.8. The test was performed with a concentration of 50 mg test item/L in 60% methanol : 40% HPLC water. Samples of the test item were analysed via HPLC on a C18 column with diode array detection. Calibration was performed using six reference items with known log POW values (given by the guidelines). The reference items were measured twice, once before and once after the measurement of the test item, for which one replicate was double injected. The void time of the HPLC system was determined with sodium nitrate. Two individual log POW values for each of the two chromatographic resolved test item signals were derived under consideration of the first and second calibration and the analytically resolved chromatographic peaks. Finally, a mean value was calculated from these individual log Pow values. The log Pow was 3.48 (peak 1) to 3.53 (peak 2) in duplicate. The partition coefficient of the test substance was determined to be log Pow = 3.48 to 3.53 at mean temperature 22.8 °C and approximately neutral pH.